“Everything is nominal on board [and] the crew is doing fine,” a translator for Russia’s Mission Control Center in Moscow repeatedly announced during a live webcast as the Soyuz MS-06 soared into the sky.

The Soyuz arrived at the space station’s Poisk module a couple minutes early on Tuesday, at 10:55 p.m. EDT, 5 hours and 38 minutes after the launch (0257 GMT on Sept. 13). “A series of burns over the next several hours will gradually raise their orbit as they chase down the space station,” NASA TV commentator Rob Navias said during the launch.

At the station, they will meet up with the other half of Expedition 53, three crewmembers who arrived at the ISS in July: NASA astronaut Randy Bresnik, Russian cosmonaut Sergey Ryazanskiy and European Space Agency astronaut Paolo Nespoli. Before they open the hatch, the crew will spend about an hour and a half performing a series of tests and checks on the Soyuz. The hatch is scheduled to open early Wednesday morning (Sept. 13) at about 12:40 a.m. EDT (0440 GMT), and a welcoming ceremony will follow. [Space Station Photos: Expedition 53 Mission Crew in Orbit]

Vande Hei, Acaba and Misurkin will spend about five months aboard the orbiting laboratory, where they will work on “hundreds of experiments in biology, biotechnology, physical science and Earth science,” NASA officials said in a statement. They will serve as members of both Expeditions 53 and 54 during their stay.

While Acaba and Misurkin have been to space before, this is Vande Hei’s first time in space. Vande Hei, who was selected for NASA’s astronaut corps in 2006, has served as an aquanaut aboard NASA’s Aquarius underwater laboratory during the NEEMO 18 mission.

Both Acaba and Misurkin have flown to the ISS before; Misurkin served as a flight engineer during Expedition 35/36 in 2013, and Acaba was a flight engineer for Expedition 31/32 in 2012. Acaba also flew on the space shuttle Discovery for mission STS-119 in 2009, and has logged a total of 138 days in space between the two missions. In total flight time, Misurkin is the most experienced, with 166 days spent in space so far.

Originally, NASA and the Russian space agency Roscosmos planned to launch only Misurkin and Vande Hei on this particular Soyuz trip. Though the Soyuz has three seats, Roscosmos decided to cut one cosmonaut post in 2016 pending the construction of a new module. To maintain a crew of six people aboard the space station, NASA extended astronaut Peggy Whitson’s stay by three months.

A Russian Soyuz rocket launches the Expedition 53 crew to the International Space Station on Sept. 12, 2017. The Soyuz carried American astronauts Mark Vande Hei, Joe Acaba and Russian cosmonaut Alexander Misurkin on a 6-hour trek to the station..

Credit: NASA TV

In February, NASA signed a contract with Boeing that would allow the space agency to fill two seats on Russia’s crewed Soyuz flights, including today’s launch and the Expedition 55/56 launch scheduled for March 2018. Boeing had obtained the seats as part of an unrelated settlement with Energia, the Russian company that builds the Soyuz spacecraft, and sold them to NASA for $373.5 million, or about $74.7 million per seat, NASA officials said in a statement. Under its regular contract with Roscosmos, NASA spends about $81.7 million per seat on a Soyuz.